Railway traffic controlling apparatus



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RAILWAY TRAFFIC CONTROLLING APPARATUS Filed May ll, 1940 14 Sheets-Sheet 4 AM EL@ .f8

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R. R. KEMMERER 2,261,388 RAILWAY TRAFFIC CONTROLLING APPARATUS A Filed May ll, 1940 14 Sheets-Sheet 6 Y lNvENToR fagyh 1Q f'emmepez? BY,A L.' HIS ATTORNEY R. R. KEMMERER RAILWAY TRAFFIC CONTROLLING APPARATUS Nov. 4, 1941.

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R. R. KEMMERER RAILWAY TRAFFIC CONTROLLING APPARATUS Filed May l1, 1940 14 Sheets-Sheet 8 INVENTOR um H15' ATTORNEY Nov. 4, 1941. R. R. KEMMERER f 2,261,388

RAILWAY TRAFFI'C CONTROLLING APPARATUS A Filed May ll, 1940 14 Sheets-Sheet 9 ?I TZ 2176A 235A E163 lNvENToR HIS ATTORNEY Nov. 4, 1941. R. R. KEMMERER 2,26388- RAILWAY TRAFFIC CONTROLLING`APPARATUS F11ed May 11, 1940 14 sheets-sheet 1o INVENTOR Ranh l2. Kemmelvep.

HIS ATTORNEY Nov. 4, 1941. R. R. KEMMERER 2,261,388

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R. R. KEMMERER RAILWAY TRAFFIC CONTROLLING APPARATUS Filed May 11, 1940 14 Sheets-Sheet 13 EDH INVENTOR lagnh R. Kemmezvegv.

HIS ATTORNEY Nov. 4, 1941. R. R. KEMMERER v 2,261,388 RAILWAY TRAFFIC coNTRoLLNG APARATUS v Filed May 1l, 1940 14 Sheets-Sheet 14 INVENTOR HU ATTORNEY Patented Nov. 4, 1941 .TENT oFfFic-E RAILWAY TRAFFIC .ooNTRoLLING APPARATUS.

Ralph R. Kemmerer, Swissvale, rla., assignor to The Union Switch t Signal- Company, Swissvale, Pa., a. corporation of Pennsylvania Application May 11, 194i), SerialtNo. 334,610

15 Claims.

My invention relates to railway traffic controlling apparatus, and it has particular ,reference to the organization of such apparatus-.into railway signaling systems of the .class whereincoded trackway energy is utilized to control either or each of the different rates of coding but one,

with the result that asthe number .of .individual frequencies employed is increased in order to obtain an increased number of signal .controls or indications, a corresponding ,increase must be made in the number of decoding units employed. This has limited to ta considerable extent the number of indications provided by .both the wayside and cab signal equipment, since it ,has been thought inadvisable to employ too numerous decoding units because of their. relatively Alarge cost of manufacture. Inaddition, the number of code frequencies available practicably for 4use is somewhat limited since relatively 4high rate codes are unsatisfactory because of the necessity of constructing code following relays which mechanically follow each individual code period. As a result of the factors mentioned above, it has been thought advisable to limit code wayside and eab signaling systems nto but 'relatively few indications, thereby requiring ,the f use of only a few individual code rates.

In view of the abovementioned and other important considerations, itis an objectpf my .present invention to provide novel and improved railway traiic controlling apparatus wherewith 'an increased number of controls may be effected through the medium of the customary few individual code rates.

Another object of my invention is the provision Vof railway tralc controlling apparatus incorporating. novel and improved means vselectivelyop- `erated by each of a plurality of distinctive codes of trackway energy constituted by coding the supply `of such energy either individually at .one or another of the customary few .code rates or in combinations of two of such code rates repeated alternately,

A further object of my invention is to jincorporate such code responsive means finto railway each distinctive combination l,o i two code rates isfutilized to control -a less restrictive 4function u than is ,controlled by veither of its two corn,- ponent codes, whereby a lfailure i".0 such appa.- ,ratus properly to respondto a combined-.code effects .the control of a more -restrictive function than is controlled by suchcornbined code.

An'addit-ional `object of my invention is -the further organization of .such ,code responsive means intoA railway trafgtlc controlling Vapparatus insuch A.manner thatv lthe particular function controlled byeach distinctivecode may be .varied by-manually operable means, ythereby v.enabling different classes of trains to `be` controlled in dif- -ferentmanners.

A still furtherpbject -of my `invention is the provision ofnoveland improved means controlled by traffic conditions in a section .for Lmodifying or changing the .Code .supplied `to the rails of the section.

Another object of my invention is the organization of railway traffic controllingl apparatus `into novel and improved .forms-lof ,railway signaling systems. A

The above-mentionedobjects, .as well as other important objects and vcharacteristicfeatures of my invention `which .will become v.readily apparent Vfrom the followingldescription, `are attained by lsupplying.tolthe yrailsof Va tracliway one or an.,- other of a plurality of different ycodesgeach of which is constitutedlby coding the `supply of trackway energyeither `at one ,orlanotherof the usual code rates individualll7 ,or at first onea n d then another Vof two -of s uch ,coderates laiternn ately. In addition, railway traiic controlling apparatusvis employed .in which a plurality A0f code. distinguishing Aor ,decoding units, one .-for each of the different individualratesof coding but one, are providedreach with additionalmeans for detecting the oomponentode ratesof each combination of two code rates applied alternatelyl and such additional means and the ,decoding units cooperate in selectively `controlling la train governing device. i f 'The Yinventionf urther consists lin the parts and in ythe arrangement and organization Yof `such parts -into railway signaling systems, aswell t be y "described more fully hereinafter.

Vtrafc controlling apparatus in such manner that 55 I shall describe a few forms of apparatusemloodying` my invention, and shall then pointout the novel features thereofgin claims.

y I nthe accompanying drawings,

Fig. '1 is aline diagramillustratingaastretch 0f4 railway track and the manner in whichwayfsi'desgnals associated .with such stretch maybe controlled by apparatus embodying my invention.

Fig. 2 is a diagrammatic view illustrating a preferred form of trackway apparatus embodying my invention when provided for a typical one of the sections represented in Fig. 1.

Fig. 3 is a diagrammatic representation of several different individual and combined codes which may be supplied to the trackway by the apparatus shown in Fig. 2.

Fig. 4 is a chart showing the conditions assumed by each decoding relay of the group shown in Fig. 2 under the several code conditions; the aspects displayed by the signals represented'in Fig. 1 for each code condition; and also the manner in which the codes represented in Fig. 3 are distributed in the sections in the rear of an occupied section for providing a six-block, sevenindication signal system embodying my invention.

Fig. 5 is a diagrammatic view illustrating a preferred form oftrain-carried apparatus embodying my invention and adapted for use in connection with a trackway provided with trackway apparatus of the type shown in Fig. 2.

Fig. 6 is a graphical representation showing typical braking-distance curves for each of three diierent classes of trains.

Fig. 7 is a diagrammatic View illustrating a modied form of the apparatus shown in Fig. 5, and also embodying my invention.

Fig. 8 `is a chart showing the manner in which the selecting means of Fig. 7 controls the aspectsdisplayed by the cab signal under the different code conditions.

Fig. 9 is a diagrammatic view'illustrating an- 4apparatus shown in Figs. 10a and 10b, andeach also embodying my invention.

Figs. 13 and 14 are diagrammatic views each showing modified forms of the apparatus illusytrated in Figs. ka and 10b, and which also embody my invention.

Fig. 15 is a diagrammatic view showing a modied form Yof the apparatus represented in Fig. 14, and also embodying my invention.

Fig. 16 is a diagrammatic View showing another modied form of the apparatus illustrated in Fig. 14, and also embodying my invention.`

Fig. 17 is a diagrammatic view which illustrates a preferred form of train-carried apparatus adapted for use in connection with the wayside apparatus represented in Figs. 10a and 10b, 13,

14, 15 or 16, and also embodying my invention.

Similar reference characters refer to similar parts in each of the several views.

Referring iirst to Fig. 1, the reference character X designates a stretch of railway track over which traic normally moves in the direction indicated by an arrow, or from left to right as viewed in the drawing. The stretch of track X `is divided by means of the usual insulated rail,

joints, into a plurality of successive adjoining track sections of which seven sections in all are illustrated. Each of the sections represented in Fig. 1 is provided adjacent its entrance end with a multiple indication railway trailc controlling signal, designated by the reference character S plus a sumx corresponding to its location. These .signals are illustrated in Fig. 1 displaying the various distinguishing indications to which they are respectively controlled in response to the presence of a train W in the extreme right-hand section P-Q of the stretch, by apparatus embodying my invention and presently to be described in detail.

The track sections of stretch X are each provided with trackway apparatus of the type required for a combined wayside and cab signal system of the frequency code type, but I shall describe in detail only the trackway apparatus provided for a typical one of such sections since it is assumed that each of the sections is provided with apparatus substantially similar to that shown in Fig.` 2 provided for the typical section P-Q. For convenience also, the same reference characters will be used throughout the description of the apparatus to designate those parts 'of the apparatus associated with other sections that correspond to the parts shown in Fig. 2 associated with section P-Q.

Referring now to Fig. 2, the rails I and la of the stretch as shown are divided by means of the usual insulated rail joints 2 to form track section P-Q and this section is provided with a track circuit, the rails of which are supplied with trackway energy through the medium of a track transformer TTQ which has its secondary winding 5a connected across such .rails adjacent the exit end Q of the section. The primary winding 6a of transformer TTQ is connected with trackway code transmitting means (not shown) located at location Q, whereby as will be pointed out presently in detail, the rails of the section are supplied with one or another of a plurality of codes, which codes are constituted by coding energy supplied to the trackway at one or another of a plurality of code rates individually or at iirst one and then another of two of such code rates alternately. I shall designate as individual codes those constituted by coding the supply of energy individually at one or another of the plurality of code rates, and shall designate as combination codes those constituted by coding the supply of energy alternately at iirst one and then another of two of such code rates. For

example, it is customary in railway signaling to employ alternating current coded or periodically interrupted at the rates of 75, and 180 times per minute and I shall use by the way of illustration in describing apparatus embodying my invention such code rates as the individual codes. A combination code is constituted by cyclically using at least two of such rates alternately. Thus `a combination code would be constituted by supplyingcurrent coded at the code rate for a predetermined interval/such as two seconds and then coded at the 120 code rate for two seconds and this combination cyclically repeated. As will be made clear presently, the trackway code transmitting means located at signal location Q for supplying energy to primary winding 6a of 4transformer TTQ is controlled by traic conditions in advance of section P-Q, and since this apparatus is substantially similar to the trackway code transmitting apparatus located at signal location P for supplying trackway energyto the rails of the section located next in the rear of the section' illustrated in Fig. 2,` only the transmitting apparatus located at signal location P is shownin the drawing.

The trackway codetransmitting apparatus located adjacent signal location P (and in like manner' the similar ,apparatus located, at Vsignal location Q) 'comprisesA a suitable .source 'of yalter- -Hating current', such vfor example as a generator notshown but.havlng its opposite terminals designated by thereference vcharacters BX and CX, :a coding device Ortransmitter CT having a plurality of continuously operating contact members, and a plurality of circuits controlled by decoding :apparatus .associated `.With `section P-.Q andlater ,to be described in detail, and by means of whichl 4.circuits-energy from the source is supplied tothe track railsof thesection .located in .the rear of section P-Q., f The Vcode transmitter CT may be any one of several suitable` types andis here shown as be Yingfof the type havingL a motor 8 which is constantly supplied with alternating current so that the transmitter is continuously active.A Motor 8 is ,operatively connected with a rotatable shaft 9, indicated by a dotted line, vupon which are secured a plurality of CamsII), II, I2 and I3. .The shaft!) is arranged to revolve inresponse to l'the actuation of motor- 8, in a counterclockwise Idirection at a constant rate, sayat 15 revo.- lutions per minute, `thereby causing the cams mounted thereon to revolve in a counterclock- Wise direction. Each of the cams is provided witha different number of teeth or projections, .cam I being shown provided, for example, with .ve teeth, cam II with eight teeth, cam I2 with twelve teeth, and cam I3 with but one tooth or projection. Transmitter CT further comprises a plurality of code contact members two members AI5 voi which are associated with cam I0, the arrangement being such that each contact member is actuated by each tooth of the cam to close contacts I5-15a and 15e-15b, respectively, and vto open such contacts between Ysuccessive teeth. lSimilarly, two contact members IZB associated With-cam II are each actuated by each tooth of cam IVI and each closes a contact I2-I20a and 12u-Inh, respectively, which contacts are `opened between successive teeth of the cam. Cam I2 also is provided with a contact .member IBD which is engaged by each tooth of the cam tov close Va Contact I80-I80a, this contact being opened between successive. teeth. Cam I3 is Aprovided with two contact members I5 which are engaged respectivelyby the single projection on .the cam to each close a contact I5-I5a, or ,IS-' -I'filr respectively, and which members each 'close another contact I5-I5c or I 5-I5d, respectively, Awhenever such membersrideon the low or funprojecting portion of the cam. It follows, therefore, that with the shaft of device CT .revolving at a .constant rate of 15 revolutions `'per minute contact 'I5-15a or I5- 15h when 'interposed ina circuit supplied with current pe- .'riodically interrupts or codes suchv current at thefrate of 75 times per minute. This coding is A'illustrated by the 75 code curve of Fig. 3, the raised portions of the curve representing the on periods during Which current iiows in the circuit and the depressed portions of the curve representing .the off periods during which no current ows. The time interval of each on 4and off period of this 75 code is substantially equal to $6 of a second.

A The 120 code curve of. Fig. 3 illustrates in a similar manner the current flowing in a circuit in` which is interposed contact I-I20a or IZB-IEM), each on and o period of this latter code being substantially' equal to '1A of a second. Likewise, the 180 code curvek of Fig. v3

represents the current iiow-ing in a circuit 'hav- 75 mina'ls .of rectifier RX; the input terminals of this rectifier `are connected to the secondary ywinding of'transiormer RT; and the .primary winding of this transformer is connected across the 'rails of `section P-Q adjacent entrancey end 'P of the section.

' The decoding means vpreviously referred to as being providedat signal location P (see Fig. 2) comprises a decoding transformer DT, a code detecting relay I-I, two decoding units DU--IZIJ and DIT-|80, twocode selecting relays BJ and AJ and three repeater relays associated ywith each of the code selecting relays.

The decoding `transfor-mer DT comprises the usual center-tapped primary Winding I8 .ha-ving a vfirst `portion thereof supplied through front contact 20 of relay TR with unidirectional currentwhich flowsfrom a suitable source, such. as a battery not shown but having. its 'opposite terminals designated by the reference characters Band C, in one direction `in the first portion of 'the winding and supplied through back contact 2l of relay TR with `unidirectional current .flow-A ing inthe other direction in the second portion of the winding. In this vmanner .is simulated the .action of alternating 'current having a frequency .equal to the rate at which relay TR. is responding to coded current. received from the rails of the section. Transformer DT further. comprises a center-tapped secondary winding I9 connected to codedetecting relay H through the medium of iront and back contacts 22 and 23, respectively, of 4relay I'R in such manner as to rectify the alternating current induced. in Winding I9 into and supply relay H withlsubstantially unidirectional current. The relay H is a direct current relay arranged and proportioned to be picked up wheneverr relay TR is following coded energy received from the rails of the section, hence such relay functions to detect whether .or not .relay .TR is4 following code. l y Y f The decoding transformerDT also supplies energy to relays .AJ and BJ through the lmedium l fofdecoding units DU-I and DU-IZl) respectively. The details of construction of the clecoding units DU-I80 and DTI-|20 are not '.'shown in the drawing, but these units usually comprise a rectiiier and a reactor condenser ,tuning unit tuned'to resonance at a frequency Acorresponding to the and to the 120 code, respectively, thereby relay AJ .is eiiectively energized and picked up when and only, when relay TRv is following 180 code, and relay BJ isA eiectively energized when and only when relay TR is following1'20 code. Preferably, the connection of decoding unit DU--I 20 with relay BJ includes a back Contact 24 ofy relay AJ, thereby insuring `vthat relay BJ will be released when relay AJ .is picked up Vin response to 180-code. v v The three .repeater relays associated withl re- .lay AJ include two slow release repeater relays -AJPI and AJPZ, yeach Vproportioned to have a slow release period slightly longer than two seconds in duration, and4 a third repeater relay AJPS. The first `slow release repeater relay AJPI is energized over anobvious circuit controlled by front contact of relay AJ and hence functions as an ordinary slow release repeater, being energized whenever relay AJ is constantly picked up or whenever relay AJ is picked up and released for alternate two second intervals. The second slow release relay AJPZ is energized over an obvious circuit controlled by back contact 26 of relay AJ and front contact 21 of repeater relay AJPI and hence functions to detect Whether relay AJ is alternately being picked up and released for two-second intervals. 'I'he third repeater relay AJPS is provided with a pick-up circuit which may be traced from term1- nal B through front contact 28 of relay AJ, front contact 29 of relay AJPI, front contact 30 of relay AJP2, and the winding of relays AJPS to terminal C. Relays AJPS also is provided with a stick circuit, in which latter circuit its own front contact 3l closes a shunt path around front contact 28 of relay AJ interposed in its pick-up circuit just traced.

Relay BJ controls two slow release relays BJPI and BJP2, each provided with a slow releasing period slightly in excess of two seconds, and another or a third repeater relay BJPS. The first slow release relay BJPI is energized over an obvious circuit including front contact 32 of relay BJ and thus' repeats relay BJ in a manner similar to the manner pointed out that relay AJPI repeats relay AJ. The second slow release repeater relay BJP2 is controlled over an obvious circuit including back contact 33 of relay BJ and front contact 34 of relay BJPI, thereby detecting if relay BJ is being picked up and released alternately for intervals each two seconds in duration. The` third repeater relay BJPS is provided with a pick-up circuit including the source of current, front Contact 35 of relay BJ, front contact 36 of relay BJPI, front contact 31 of relay BJP2, and the Winding of relay BJPS. The latter relay also is provided with a stick circuit in which its own front contact 3B closes a shunt path around front contact 35 of relay BJ in the previously traced pick-up circuit of the relay.

The decoding apparatus above described functions to selectively control, in a manenr to be pointed out in detail presently, the wayside signal provided for the associated track section. Such signal may take any one of many wellknown forms of railway signaling devices, but is shown in Fig. 2 (see signal SP) for the sake of illustration as comprising three individual color light units disposed one above the other on the associated signal mast. Each of the units, which I shall refer to as units Ul, U2 and U3 in accordance with ltheir respective positions on the signal mast with unit UI located at the top of the mast, comprises a red lamp R, a yellow Y and a green lamp G.

The decoding apparatus further cooperates with its associated code transmitter CT to selectively control in accordance with traffic conditions, the supply of trackway energy to the track rails of the section next in the rear. The manner in which the control of the associated signal and the supply of trackway energy to the rails of the section next in the rear are effected by apparatus embodying my invention will best be understood from the following description of the operation of the apparatus as a whole. In such `description,the apparatus represented in Fig. 2 will be assumed to correspond to the similar apparatus provided foreach of the sections represented in Fig. 1, and the operation of the apparatus as a whole will be described by tracing in Fig. 2 'the various circuits that are set up .by such or corresponding apparatus in response to each of the different code conditions in the trackway. To facilitate this description, reference will also be made to Fig. 4 wherein there is set forth in chart form the various codes received and sent (columns ,f and g, respectively, of Fig. 4), by the Wayside apparatus at each signal location; the aspects displayed by each unit ci the various signals (columns b, c and d of Fig. 4); the positions assumed by each of the various relays comprising the decoding apparatus located at the several signal locations (columns y to p, inclusive); and the meaning of the various aspects displayed by the signals (column e). i

As can be seen in Fig. 1, section P-Q is occupied by a train W so that trackway energy is shunted away from the track relay of such section. From column ,f of Fig. 4, it can be seen that the apparatus at signal SP receives no code, and columns i through p, inclusive, of Fig. 4 indicate that all decoding relays are released; the released and picked-up positions of the decoding relays being indicated in Fig. 4 by representing the armatures associated with such relays in a dropped-away or picked-up position, respectively. Also, it can be seen that each unit of signal SP displays its red aspect (see columns b, c and d of Fig. 4) and that 15 code (see column g of Fig. 4) is transmitted to the next section to the rear.

Referring now to Fig. 2, the wayside apparatus there illustrated is shown in the condition responsive to a train W occupying its associated section. In this condition of the apparatus, relay TR is inactive and all of the decoding relays are released as shown in Fig. 2 and as set forth in the table of Fig. 4.

With the decoding relays located at signal location P all released, lamp R of unit UI of signal SP is provided with an energizing circuit which may be traced from terminal B through back contact 40 ofrelay H and the filament of lamp R of unit UI to terminal C. Lamp R of unit U2 of signal SP likewise is provided with an energizing circuit passing from terminal B through back contact 4l of relay H and the filament of lamp R of unit U2 to terminal C; and similarly lamp R of unit U3 of the signal is provided with an energizing circuit passing from terminal B through back contact 42 of relay H and the filament of lamp R of unit U3 to terminal C. It follows, therefore, that each unit of signal SP displays its red aspect, which denotes that its associated section P-Q is occupied by a train.

Also, a circuit is completed for supplying 15 code trackway energy to the rails of the section next to the rear of section P-Q, that is, section O--P. This circuit may be traced from terminal BX through contact 15--15a of transmitter CT, back contact 43 `of relay H and primary winding 6 of transformer TT, which transformer has its secondary winding 5 connected across the track rails ofthe section next in the rear, to terminal CX.

When 15 code is supplied to the rails of section O-P, relay TR associated with that section is operated at this rate and its associated relay H is energized (see columna of Fig. 4, but all other1 decoding relays are released. The energization of relay H establishes a circuit for lamp Y of unit U3 of signal SO, which circuit may be traced in Fig. 2 from terminal B through front contact` 44 of relay H, back contact 45 of relay AJPl and the filament of lamp Y of unit U3 to terminal C. Unit UI of. signal SO' now is caused to display its' red aspect over a circuit which may be traced from terminal B through front contact 54 of relay H, back Ycontact 45 of relay AJPS,L back contact 41 of relay AJPI, back contact 48 of relay BJPS and the iilament of lamp R of unit UI to terminal C. Also, unit U2 of signal SO isV caused to display its red aspect over a circuit passingfrom terminal B through front contact 49 of relay H, back contact 50 of relay AJPS, back contact 5I of relay AJPI, back contactv 52 of relay BJPS', back contact 53 of relay BJPI and the filament of lamp R of unit U2 to terminal C. Signal SO therefore displays a red over red over" yellow aspect, which indicates that one clear block intervenes between the signal and the next occupied block. In addition, with relay H picked up, |20 code trackway energy is supplied to the section N-O over a circuit which may be traced from terminal BX through contact {2U-[20a of transmitter CT, back contact 55 of relay BJPI, back contact 5B of relay BJPS, back contact 51 of relay AJPI, back contact 58 of relay AJPS, frontl contact 59 of relay H and primary winding 6 of transformer TT toY terminal CX.

The 12B code supplied to section N-O causes the track relay of section N-O to operate at a corresponding rate and as a result relays H, BJ and BJPI associated with signal SN of that` section are picked up (see columns and p of Fig. 4). The picking up of relay BJPI controls lamp Y of unit U2 of signal SN to its lighted indication over a circuit which may be traced in Fig. 2 from ter-` minal B through' front contact 4B of relay H, back contact 5U of relay AJPS, back'contact 5l of relay AJPI, back contact 52 of relay BJPS,

front contact 60 of relay BJPI and the lament of lamp Y of unit U2 to terminal C. The energizing circuits for the lamps of units Ul and U3 of signal SN are similar to those previously traced for corresponding units of signal SO, and consequently signal SN displays a red over yellow over yellow aspect, indicating that two blocks are clear between the signal location and the Inext occupied block. Also, with relays H and BJPI associated with section N-O picked up, section M-N is supplied with |20-15 code trackway energy by virtue of the action of contacts l5-v-l5b and -l5-l-5d of transmitter CT, these contacts functioning to cause |20 code and 15 code to be supplied alternately for successive intervals each'of two seconds in duration.- During the intervals that .contact I5-I5b of transmitter CT is closed, the' rails of section M,Nv are supplied with l2llV code over a-circuit .which extends from terminal BX through contact |2lll20b of transmitter CT, contact..I.5-I5b of transmitter CT, front contact 64 of relay BJPI, back contact 56- of relay BJPS; back contact 51 of relayyAJPl, back contact53 of relay AJPS, front contact 5910i relay H, and'primary vwinding 6 of transformer TT to terminal'C. Then, during the alternate intervals that transmitter CT closes contact I5-I5d, 15' code is'supplied to the rails of section M-N over a circuit which extends "from terminal BX through contact 15--15b of transmitter CT, contactfl5-ri5d of transmitter CT, front contact 64 of Vrelay BJPI, and then passing from contact 64 of relay-BJPI through the circuit corresponding to the circuit just traced from such contact for |20 code. Curve |20-15 of Fig. 3 represents the current ow in the above circuits by means of which |20 and 15 code are recurrentlysupplied for alternate in-` tervals of two seconds each to the rails of section M-N to provide a |20-15 combined code. v,

In response to the |20-15 code supplied to section M-N, decoding relays H, BJPI BJP2 and BJPS associated with section M-N are energized (see table Fig. 4). Relay H of section M--N is energized by virtue of relay TR ofV that section following code. Relay BJ is energized during the alternate intervals of two seconds that relay TR follows |20 code and is released during the intervals that relay TR follows 15 code.4 Relay BJPI is `energized during each interval that relay BJ is picked up, and by virtueof its slow releas- .BJ-P S is held up over its stick circuit as long as relay'BJ is alternately picked up andreleased t` maintain bothfrelays BJPI and BJP2 energized,A v i With the decoding apparatus located at signal SM responding in the above described manner to the combined |20- 15 code, each unit of signal SM `is controlled to `display its yellow aspect. Lamp Y of unit Ul of signal SM is energized over a circuit which may be traced in Fig. 2 from terminal B through. front contact 54 of relay H, back Contact 46 of relay AJPS, back contact 41 of relay AJPI, front contact l62 of relay rBJPS andl the lament of lamp Y of unit UI to terminal C. Lamp Y of unit U2 of signal SM is energized over a circuit which extends from terminal B through front contact 49 of relay H back contact 50 of relay AJPS, back contact 5I of relay AJPI, front contact 63 of relay BJPS and the lament of lamp Y of unit U2 to terminal C; vand lamp Y of unit U3 is energized over a circuit extending from terminal B through front Contact 44 of relay H,A back contact 45 of relay AJPI and the lament of lamp Y of unit U3 to terminal C. Signal SM in displaying a yellow over yellow over yellow aspect indicates that three blocks are clear between the signal and the nextoccupied block.

In addition, the decoding apparatus located at signal SM causes code to be supplied to the rails of the next .adjacent section to the rear, section L M. This energy is supplied over a circuit extending from terminal BX through contact 18H-480m of transmitter CT, front contact65 of relay BJPS, back contact 51 of relay AJPI, vback contact 58 of relay AJPS, front contact 59 of relay H and primary winding 6 of transformer TT to terminal CX.

In response to the supply of |30 code to section L--M, relays H, AJ and AJPI located at signal location SL are picked up. It should be noted that relay BJ cannot respond to code inasmuch as itsv energizing circuit is open at back contact 24 of relay AJ. With relays'y H, AJ and AJPI energized, lamp G of unit U3 of signal SL is illuminated over a circuit which may be traced in Fig. 2 from terminal B through front contact 44 of relay H, front contact 66 of relay AJPI, and the iilament of lamp G of unit U3 to terminal C. Lamps Y of units UI and U2 of signal SL also are illuminated, the circuit for lamp Y of unit Ul passing from terminal B through front contact 54 of relay H, back contact 46 of relay AJPS, front contact 61 of relay AJPI and the filament of lamp Y of unit UI to terminal C; and the circuit for lamp Y of unit U2 extending from terminal B vthrough front contact 49 of relay H, back contact 50 of relay AJPS, front contact 68 of relay AJPI and the filament of lamp Y of unit U2 to terminal C. Signal SL thus displays a fyellow over yellow over green aspect, indicating the presence of four clear blocks between the signal and the neXt occupied block.

Section K-L located next in the rear of section L-M is supplied with trackway energy formed into a code combination comprising alternate two-second intervals of |80 and 15 code, by circuits established by the decoding apparatus associated with section L M. |80 code is supplied to the rails of section K-L during the alternate intervals each of two seconds in duration that contact |5a-l5 of coder CT is closed and a circuit is completed from terminal BX through contact |80|80a of transmitter CT, contact |5a|5 of transmitter CT, iront contact 'I0' of relay AJPI, back contact 58 of relay AJPS, front contact 59 of relay H and primary winding 6 of transformer TT to terminal CX. '|5 code is supplied to the rails of section K-L during the other two-second intervals that contact |5|5c of transmitter CT is closed and contact |5a|5 of transmitter CT is opened, over a circuit extending from terminal BX through contact '|5-15a of transmitter CT, back contact of relay AJPS, contact |5c|5 of transmitter CT, front contact 10 of relay AJPI, back contact 58 of relay AJPS, front contact 59 of relay H, and primary winding 6 of transformer TT to terminal CX. Curve |80`|5 of Fig. 3 represents the current supplied to section K-L over the circuits just traced for this combination code.

The supply of ISU-'l5 code to the rails of section K--L causes decoding relays H, AJ, AJPI, AJP2 and AJPS associated with that section to be picked up. Relay H of section K-L is picked up in response to relay TR following code; relay AJ is .energized during the alternate two-second intervals that relay TR responds to |80 code and is deenergized during the intervals that relay TR follows |5 code; relay AJPI is energized during each two-second interval that relay AJ is picked up and relay AJPI remains picked up by virtue of its slow releasing characteristics during the alternate intervals that relay AJ is released; relay AJP2 is energized over front contact 2`| of relay AJPI during each two-second interval that relay AJ is released, and the slow releasing characteristics of relay AJP2 maintain that relay picked up during the alternate picked-up periods of relay AJ; and relay AJPS picks up to complete its stick circuit after both relays AJPI and AJP2 become picked up in response to the alternate picking up and releasing of relay AJ.

Signal SK is controlled to display a yellow over green over green aspect, thereby indicating iive clear blocks between the signal and the next occupied block, by virtue of the response of the decoding apparatus located at signal localay follows |20 code.

tion SK to the combined |-15 code. The decoding apparatus located at signal SK controls that signal to display the above-mentioned aspect by illuminating lamp Y of unit UI over a circuit which may be traced in Fig. 2 from terminal B through front contact 54 of relay H, front contact '|2 of relay AJPS, back contact 13 of relay BJPS and the ilament of lamp Y of unit U| to terminal C; by setting up a circuit including front contact 49 of relay H, front contact '|4 of relay AJPS and the ilament of lamp G of unit U2 whereby that lamp is illuminated; and by completing a circuit including front contact 44 of relay H, front contact 66 of relay AJPI and the filament of lamp G of unit U3 of signal SK whereby that lamp is illuminated.

The rails of section J-K are supplied by the decoding apparatus and code transmitter located at signal location SK with trackway energy formed of alternate intervals of |80 and |20 code. During the intervals that contact |5|5a of transmitter CT is closed, the rails of section J--K are supplied with |80 code over a circuit which extends from terminal BX through contact |80|80a of transmitter CT, contact |5a|5 of transmitter CT, front contact of relay AJPS, front contact 59 of relay H and primary winding 5 of transformer TT to terminal CX. Then, during the alternate intervals of two seconds each that contact |5|5c of transmitter CT is closed, the rails of section J--K are supplied with |20 code over a circuit extending from terminal BX through contact |20|20a of transmitter CT, front contact '|8 of relay AJPS, contact |5c|5 of transmitter CT, front contact l1 of relay AJPS, front contact 59 of relay H and primary Winding 6 of transformer TT to terminal CX. The current ilowing in the rails of section J-K by virtue of the above-mentioned circuits is represented by the combination code curve IBD-|20 of Fig. 3.

In response to the supply of |80|20 code to the rails of section J-K, all the decoding relays located at signal location SJ are picked up and each unit of signal SJ is caused to exhibit its green aspect (see table of Fig. 4). Relay H associated with section J-K is picked up in response to the associated track relay following the combined|80|20 code, and relays AJ and BJ are picked up and released, respectively, during the two-second intervals that the track relay responds to |80 code and such relays are released and picked up, respectively, during the alternate twosecond intervals that the track re- The repeater relays AJPI, AJP2, AJPS, BJPI, BJP2 and BJPS accordingly are all energized and are picked up in response to the alternate picking up and releasing of the two code selecting relays AJ and BJ caused by the track relay following the combined |80I20 code. With all the decoding relays associated with section J-K picked up, lamp G of unit UI of signal SJ is energized over a circuit which `may be traced in Fig. 2 from terminal B through front contact 54 of relay H, front contact 12 of relay AJPS, iront contact 19 of relay BJPS and the lament of lamp G of unit Ul to terminal C; and lamps G of units U2 and U3 of signal SJ are energized over circuits corresponding to the circuits previously traced for corresponding lamps of ysignal SK.

In addition, the apparatus located at signal location SJ causes trackway energy of ISU- |20 code to be supplied to the section next in the rear, over circuits controlled by the decoding 

